1. Field of the Invention
The present invention relates to a directional microphone module and a telephone handset for a portable telephone and the like provided with the module.
2. Description of the Related Art
A telephone handset is integrally formed of a transmitter including a microphone and a receiver including a speaker. For convenience of operation, some handsets lately developed are provided thereon with a switch portion, including a dialing means and the like. In portable telephones and cordless phones, the power source and transmission/reception circuits are incorporated in the handset itself. In order to obtain a compact telephone handset of the described type, if the transmitter and the speaker in a handset are brought close to each other, then, since the handset is generally used with the receiver held in contact with the ear, the transmitter of the handset is brought away from the mouth and, hence, the N/S characteristic of the transmitter is deteriorated. Therefore, it is difficult in general to obtain both the advantages, compactness of the handset and a good S/N characteristic of the transmitter, at the same time and, accordingly, there are demands for a telephone handset by which both the advantages are obtained at the same time.
There has so far been proposed an arrangement to use a directional microphone in the transmitter to improve the S/N characteristic of the transmitter of a compact telephone handset in which the transmitter and the receiver are set close to each other. By the use of such directional microphone, it is expected that sounds other than the voice made by the operator will not be collected by the microphone and the S/N characteristic of the transmitter will thereby be improved.
However, the directional microphone is such that exhibits good directivity only when the microphone is disposed in a free space and does not exhibit good directivity when it is disposed within a closed, small case such as a handset. Accordingly, a good S/N characteristic of the transmitter cannot be attained by mere mounting of a directional microphone in the transmitter portion.